Although it mentions the original Electric Mistress, it is a very particular pedal. It's actually has the flanger and chorus effects, but at the same time. You can mix the amount of each one of the effects you want, and their modulation speeds is (somehow) synchronized.
If you take each one of the effects separately, they are very good sounding on their own, rich and organic. But each one is very strict in terms of tweaking possibilities: just one knob (mix).
But what is really cool about this pedal is that you can blend in both effects and create a completely new sound. These blended sounds can be really great.
The speed knob is also something to be carefully explored. Some settings sound great at fast modulation speeds and awful at slow frequencies. You can get really interesting rotary speaker simulations at high modulation speeds. I recommend a search on Youtube for a video of Bill Ruppert exploring this pedal. I don't use the fixed filter settings, as they're just not useful for me.
Overall, it takes some time until you can really understand this pedal. After that, you have a really interesting tool to create very personal and pleasing chorus/flanger textures.